Automatic livestock weighing system

ABSTRACT

A system for weighing a plurality of quadruped animals is for use in a pen confining the animals. The pen has at least first and second segregated spaces with a first one-way chute allowing animal passage from the second space to the first space. A weighing station is located within a passage having an entrance and an exit, and that allows animal passage from the first area to the second area. The weighing station includes a weighing platform within the passage over which an animal must pass when passing from the first to the second space. The weighing platform has inlet and exit scales that support the weighing platform adjacent to inlet and exit ends thereof, and provides inlet and exit weight signals. A controller receives the inlet and exit weight signals and uses them in an iterative process to determine the presence of a single animal on the weighing platform. Once that determination is made, the sum of the inlet and exit weight values is very likely to accurately provide the animal weight. The controller may also use the inlet and exit weight signals to control closing of an inlet gate to bar more than one animal at a time from the weighing platform. An animal sorting system can easily incorporate this weighing system to provide more accurate sorting.

BACKGROUND OF THE INVENTION

1. Scope of the Present Invention

The present invention relates to the field of management of quadrupedlivestock such as pigs based on measured weight. More specifically, thepresent invention provides an apparatus and system for weighinglivestock and provides the possibility for accurate sorting thelivestock according to weight.

2. Background of the Prior Art

Livestock producers now feed the livestock in large automated facilitiesholding literally hundreds or thousands of animals. An important aspectof efficient livestock production is determining the weight ofindividual animals in a herd. Animals should be shipped for slaughter attheir optimal weight. The animal may not grade as well as possible andfeed wasting occurs if an animal is fed too long. If fed for too short atime, an animal may again not grade as well, and the chance to addvaluable weight to the animal relatively cheaply at the end of theprocess is lost.

These considerations are pertinent in pork production. Pigs gain weightrelatively quickly as a percentage of body weight. Weight gains varysubstantially from pig to pig. A wrong guess as to weight for anindividual pig can be costly when measured as a percentage of theselling price. In fact, estimates suggest that additional profit of atleast $20.00 per pig is possible by carefully measuring individual pigweight and basing feed selection and shipping decisions on these weightmeasurements.

The present invention relates to an apparatus and system that can moreaccurately and reliably track weight changes in individual members a pigherd. This information allows producers to improve weight gainefficiency through sorting by weight for feed mixture and for selectingand scheduling pigs for shipping to slaughter.

Now, every animal weighing system has a way to control access to theweighing station so that only one animal at a time enters the station.Typically, the system has an inlet gate controlled by the system thatcloses when an animal has passed through the gate. The gate usuallyoperates pneumatically or hydraulically.

To reduce the chance of more than one pig entering the weighing systemat a time, the system must accurately sense when a single animal haspassed through the gate, and only then close the gate. The gate shouldnot close on the animal because that may agitate or annoy the animal,deterring the pig from again passing through the weighing system andaffecting weight gain. Those familiar with livestock such as pigs knowthat unpleasant experiences with a particular area of the confinementspace will train the livestock to avoid the area, resulting in fewerweighing events for the affected livestock.

Some current systems rely on a sensor such as an animal proximity sensorthat initiate the closure of the inlet gate upon sensing an animalpassing through the inlet gate. Others use an operator-programmedtrigger weight on the weighing platform for this purpose.

Both of these systems have inherent problems. Either type of sensingelement requires frequent adjustment during the growth of the animals inthe herd to reliably sense presence of a single animal. Each may fail towork properly when there is a large variation in sizes or weights ofpigs in the herd.

A further problem is simply that of reliability. Livestock pens areinherently dirty places with dust and corrosive manure and urinethroughout. Livestock feeders now frequently wash the sites such aswatering, feeding, and weighing stations where animals tend tocongregate. The water spray during washing can easily damage sensitiveelectronic components of all kinds. Separate components for sensinganimal presence in the weighing station simply provides one morepotential failure point.

For accurate weight measurement, systems now typically use two weighingelements supporting the weighing platform as shown in FIGS. 2-4. Oneweighing element is at the inlet or entry point for inlet and another atthe exit. Load cell 35 in FIG. 2 senses inlet point weight and load cell36 senses exit point weight.

Current systems sum the two values provided by the load cells as theanimal enters the weighing platform. The average for the sum a number ofsamples accurately indicates animal weight.

SUMMARY OF THE INVENTION

While weighing the animals in a herd, it is advantageous to sense theposition of livestock on the weighing platform of an animal scale. Oncethe position sensing indicates that the animal is completely on thescale, one can infer that weighing the animal will be successful.

The present invention provides a weighing system with an ElectronicSense of Position (ESP) feature that uses the relative amounts of weightsensed on scales fastened at inlet and exit ends of the weighingplatform to act as an animal position sensor. This feature is able todetect the position of a domestic animal such as a pig on a weighingplatform and the movement of the animal onto and off the weighingplatform.

The ESP feature enables proper operation of any gates controlling accessto the weighing platform based on the position of the livestock, bydetecting all four feet on the scale. The ESP feature detects livestockposition by testing the weights at the inlet and exit of the weighingplatform. The ESP feature also allows the sensed animal weight to beverified as accurate.

The present invention is usable with a system for sorting a herd ofanimals such as pigs based on a user-programmed weight. The system canalso be used to log individual animal weights by a unique identificationnumber as read from the animal's ear tag to allow tracking individualand group animal performance.

The system consists of an electronic controller, system softwareexecuted by the controller, an enclosed weighing platform with controlpanel and a pneumatic-controlled inlet gate and possibly an exit gate. Aconsole with display and keypad and a radio frequency ear tag reader iscustomary as well.

The system software operates the scale by actuating the pneumatic gateor gates, weighing the animal, storing the data, and providing the userwith the weights of the animals in the herd.

The user can accommodate the size of animals in the herd by adjustingthe closing force and the speed of the inlet gate. This systemeliminates the need to adjust animal sensors at the inlet gate. Settingan overweight limit perhaps 10% above the heaviest animal in the herdallows the system to detect two animals in the weighing station.

The system software makes a continuous log of the livestock groupautomatically. The log includes values such as lightest, heaviest,average, and total weights. It can also record the number of animals,standard deviation, and average daily gain from the previous day. Inaddition to the previous information, it can also display a histogram ofthe distribution of weights. This histogram is adjustable and gives theuser the ability to zero in on marketing opportunities. The system caneasily track death, sales, and other pig inventory changes.

The system software needs no preprogramming to collect information.Information logs automatically and is accessible later.

In one form, this system for weighing a plurality of quadruped animalsis usable in a pen confining the animals. The pen has at least first andsecond segregated spaces with a first one-way chute allowing animalpassage from the second space to the first space.

A weighing station is located within a passage having an entrance and anexit, and that allows animal passage from the first area to the secondarea. The weighing station includes a weighing platform over which ananimal must pass when moving from the first to the second space.

The weighing platform has inlet and exit ends adjacent to the first andsecond spaces respectively. An inlet scale supports the weighingplatform adjacent to the inlet end thereof, and provides an inlet weightsignal encoding a value indicating the weight supported by the inletscale. An exit scale supports the weighing platform adjacent to the exitend thereof and provides an exit weight signal encoding a valueindicating the weight supported by the exit scale.

A controller receives the inlet and exit weight signals. In oneembodiment the controller comprises a memory for storing valuesassociated with weighing an animal as well as for storing object codefor execution by the controller.

The controller has a calculation element receiving and recording theinlet and exit weight signals, calculating a plurality of parametersbased on the inlet and exit weight signal, and encoding a scale weightvalue equal to the sum of values encoded in at least one inlet weightsignal and at least one exit weight signal.

The controller also has a platform status element periodically executingan algorithm determining from the values encoded in the inlet and exitweight signals the presence of a single animal on the weighing platform,and responsive to said determination issuing a weight captured signalsignifying that the scale weight value accurately specifies the weightof the animal on the scale.

A system sorting animals according to weight can incorporate thisweighing system. This weighing system can allow a user to select athreshold weight from a histogram, or distribution of animal weights ina herd, when sorting the herd. The weighing system is compatible withsoftware that can generate an approximation of the precise histogrambased on the animals actually crossing the scale over time. The weighingsystem can associate weights with individual animal RFID tags.

This weighing system can rapidly and accurately weigh large numbers ofanimals. Not every animal crossing the weighing platform will beaccurately weighed, although the percentage weighed successfully islikely to be upwards of 90%. However, the system is very successful atidentifying weights likely to be inaccurate.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a plat or plan (bird's eye) view of a representative animalpen in which the weighing station of the invention may be used.

FIG. 1 a shows an alternative structure for the exit of the weighingstation.

FIG. 2 is a side view schematic of the weighing station.

FIG. 3 is a perspective view of the weighing station.

FIG. 4 is a side view labeling a weighing station dimension.

FIG. 5 is a flowchart of software whose execution by a microprocessor orother computer creates a calculation element that reads the W_(i) andW_(e) values and calculates a number of parameters based on theseindividual values.

FIGS. 6 a and 6 b show a flowchart of software whose execution by amicroprocessor or other computer forms part of a platform status elementthat senses animal position and prevents an animal on the weighingplatform from leaving the weighing platform.

FIGS. 7 a and 7 b show a flowchart of software whose execution by amicroprocessor or other computer forms part of a platform status elementthat tests animal weight and sets a flag verifying that the weightsensed for the animal is likely to be accurate.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 shows a representative barn or pen 10 for holding a plurality ofanimals to be fed for weight gain preparatory for slaughter. The animalsin this example are shown as pigs 20 a, 20 b, etc., but the weighingsystem can be adapted to weigh individual animals in herds comprising avariety of quadruped livestock. The weights may vary substantially, ormay all be reasonably similar. For a high percentage of successfulweighing events, the animal weights should not have too great a range.

As pigs 20 a, etc. grow, their weights will increase from as little as30 lb. to as much as 300 lbs. (approximately 14 to 140 kg.) with theirlengths increasing proportionately. This invention can easily handlesuch a wide range of weights and lengths. The user may need to makeoccasional adjustments as the animals 20 a etc. grow to maintain a highpercentage of successful weighing events.

Pigs 20 a, etc. may have RFID tags 21 attached to the pigs 20 a, etc.that uniquely identify the pigs 20 a, etc. to which the tags 21 areattached. RFID tags 21 allow weights to be associated with individualpigs 20, etc.

A fence 12 divides pen 10 into a feeding (second) space 15 and a loafing(first) space 14. Feeding space 15 has both a water trough 16 b and afeed trough 13. The loafing space 14 has a water trough 16 a only,although this configuration may be changed to encourage animals tofrequently move between spaces 14 and 15.

Pigs 20 a, etc. can only pass from loafing space 14 to feeding space 15through a passage 31 having a floor 28 (FIG. 2) above which a weighingstation 33 is positioned. Panels form the sides of passage 31. Weighingstation 33 includes a weighing platform 42 (FIGS. 2 and 3) on which apig 20 a must be standing or lying when recording its weight.

FIG. 1 shows an inlet gate 40 controlling animal entry to passage 31 andweighing station 33. Inlet gate 40 has a pneumatic actuator thatoperates gate 40 between open and closed positions. Gate 40 may haveother types of actuators such as hydraulic or electrical.

Inlet gate 40 should be close to the inlet end of weighing platform 42.A typical gate 40 may have adjustable closing speed and force. Lightpigs 20 a (say 30-100 lb.) will require gate 40 to have a slower andless forceful closure than large pigs 20 a. The industry is familiarwith these factors.

The inlet gate 40 open position allows passage of a pig 20 a fromloafing space 14 to passage 31 and weighing platform 42. The inlet gate40 closed position prevents passage of an animal between loafing space14 and weighing platform 33. Inlet gate 40 shifts to the open positionresponsive to a first value of an inlet gate signal, and shifts to theclosed position responsive to a second value of the inlet gate signal.The gate 40 actuator opens and closes gate 40 responsive to the inletgate signal.

In one form of this invention, pigs 20 a, etc. leave weighing station 33through a first one-way chute 32 that allows pigs 20 a, etc. to easilypass from loafing space 14 to feeding space 15 but bars them frompassing in the opposite direction. Alternatively, FIG. 1 a shows an exitfor passage 31 comprising an exit gate 41 whose operation is similar tothat of inlet gate 40. Exit gate 41 shifts between open and closedpositions responsive to first and second values of an exit gate signal.

Pigs can only reach the loafing space 14 from feeding space 15 through asecond one-way chute 25 similar to one-way chute 32, and shown with apig 20 e about to enter chute 31. A number of commercially availableone-way chutes 32 and 25 are suitable for this purpose.

Of course, more than one second one-way chute 25 may be used when largernumbers of animals 20 a, etc. are housed in pen 10. The invention worksoptimally when animals 20 a, etc. can move freely from space 15 to space14.

Normally, one expects a pig 20 to first step onto weighing platform 42with one front hoof as shown in FIG. 2. After a time typically taking afew seconds but ranging from less than a second to tens of seconds, pig20 moves to a second position 20′ shown in phantom where all four hoovesare on weighing platform 42.

The weighing platform 42 shown in FIG. 3 is rectangular and hung from aninlet bar 70 and an exit bar 71 respectively by cables 64 and 74separated by a distance L as shown in FIGS. 3 and 4. In a weighingsystem for pigs, L may be 4 ft. (1.2 m.). Platform 42 has an inlet endadjacent to loafing area 14 and an exit end adjacent to feeding area 15.An inlet load cell or scale 35 and an exit load cell or scale 36 suspendthe respective bars 70 and 71 from an overhead support 68. Bars 70 and71 may incorporate their respective in scales 35 and 36 as in integralcomponent such as a strain gauge.

As seen in FIG. 2, inlet scale 35 and exit scale 36 provide inlet andexit weight signals on paths 35 a and 36 a that respectively encodeweights W_(i) and W_(e) sensed by the scales 35 and 36. Arrow 65 inFIGS. 2 and 3 indicates the direction of pig 20 a, etc. movement acrossweighing platform 42.

A controller 30 shown in FIG. 2 comprises a microprocessor mountedwithin a housing with multiple I/O connections. Controller 30 is thecontrol center of the system and receives the inlet and exit weightsignals on signal paths 35 a and 36 a respectively. The circuitry ofcontroller 30 includes a memory 62 for data and software storage and ananalog-to-digital converter that translates the inlet and exit weightsignals into usable digital values and stores these in the memory.

Controller 30 controls the position of gate 40 (and gate 41 if present)with gate signals carried on paths 65 and 66. An antenna 50 providescontroller 30 with radio frequency ear tag signals on a path 50 a.

The gate signals to gates 40 and (if present) 41 that controller 30provides depend on the values of W_(i) and W_(e). Controller 30 samplesthe inlet and exit weight signals about every 100 ms. This frequentsample rate allows controller 30 to use changes in the individual valuesof W_(i) and W_(e) to estimate the position of pigs 20 a, etc. onweighing platform 42 and determine when pigs 20 a, etc. have all fourhooves on platform 42.

The system software in controller 30 provides the algorithms and processcontrol mechanisms for operating the system. The controller 30 usesoperator-entered parameters to automatically collect and verify animalweight information.

A user console not shown, which can be remote from the controller 30,provides a means for an operator to view and enter data. Informationtransfers between the user console and the controller 30 through acommunication cable. Operator settings entered at the user console arestored in memory 62.

Controller 30 may include an ear tag reader 63 capable of reading animalear tags 21 with antenna 50 while the animals 20 a, etc. are containedin passage 31. Upon receiving the ear tag information on path 50 a,controller 30 automatically transmits the identification number recordedtherein to memory 62 where the animal weight and other pertinentinformation can be stored with it.

One of the unique aspects of the invention is the closing of the inletgate based on hog weight and position. This is made possible by sensingthe inlet weight W_(i) separately from the exit weight W_(e) andcalculating a number of parameters based on W_(i) and W_(e). W_(i) andW_(e) values are read separately in a multiple channel analog-to-digitalconverter.

Controller 30 uses the separate W_(i) and W_(e) values to calculate thelocation (position) of the center of mass of the pig 20 a, etc. on theweighing platform 42. This enables the controller 30 to close the inletgate 40 when the pig 20 a has all four hooves on the weighing platform42. Closing the inlet gate 40 prematurely will result in the animalbeing pinched, stressing the pig 20 a, etc. and causing it to avoidpassage 31, and hence rarely weighed.

The software of the present invention uses one of two detection schemesto trigger the closing of the inlet gate 40. Each of schemes initiateinlet gate 40 closure when pig 20 a has the proper location on theweighing platform 42.

Scheme 1 monitors the pig entrance onto the weighing platform 42 byfirst detecting the front hooves on the weighing platform 42 and whendetecting the back hooves on the weighing platform 42, triggers the gateclosure. Detecting the front hooves separately from the back hooves isdone without knowing actual pig position.

Scheme 2 uses pig weight and position to trigger the gate closure. Aunique algorithm combines published information of pig body lengthversus body weight and front hoof weight versus body weight to providethe average front hoof weight versus body length. A lookup table wasproduced from this algorithm that associates the required pig positionwith the sensed pig 20 a weight W_(i)+W_(e). The internal software ofcontroller 30 uses this lookup table to initiate the closure of inletgate 40 when the pig position exceeds the look-up table trigger positionfor the pig 20 a weight.

FIGS. 5-7 b comprise software flowcharts that outline the logic of thesedetection schemes. The reader should be aware that these flowchartelements have physical manifestations in the patterns of the matterwithin memory 62 that record the object code for these softwareelements. In particular, various of the activity elements can set theinlet gate flag to values that control the inlet gate 40 position.

In general in the flowcharts of FIGS. 6 a-7 b, the decision elements,and the activity elements that set flags and acquire the W_(i) and W_(e)values, form a platform status element within controller 30. Activityelements that perform various arithmetic operations such as those inFIG. 5, form part of a calculation element within controller 30.

A software manager, not shown, coordinates the selection of routines forexecution. Instruction execution generally starts at the “AnimalCapture” entry point 100. The various routines of FIGS. 6 a-7 b run inan infinite loop with execution returning to entry point 100 when anynumber of different conditions are detected by the software execution.

With respect to the Acquire Weight Data (AWD) routine in FIG. 5 however,the software manager tracks elapsing time and at preselected intervals,transfers execution to the AWD routine. In one embodiment, the AWDroutine executes every 95 ms.

The AWD routine shown in FIG. 5 reads the weight data W_(i) and W_(e)from scales 35 and 36 and computes a number of parameters based on theweight data. The AWD connector element 90 is the entry point to the AWDroutine. The first component of the AWD routine is an activity element92 that saves as the previous values, the current values of a ScaleWeight value SW, a Scale Weight summation value ΣSW, the W_(i) value,and the W_(e) value in memory 62 locations for the previous SW, ASW,W_(i), and W_(e) values.

Next, activity element 94 instructions read the weight values encoded onpaths 35 a and 35 b and convert them to current digital values W_(i) andW_(e). The current W_(i) and W_(e) values are then stored in the memory62 locations for the current W_(i) and W_(e) values.

Then activity element 96 computes and stores in memory 62 a number ofparameter values based on the W_(i) and W_(e) values. Element 96calculates from the current values of W_(i) and W_(e), current values ofSW=W_(i)+W_(e); ΣSW value=previous ΣSW value+current SW; a ΔSWvalue=|current SW−previous SW|/previous SW; and a pig position (PP)value=W_(e)/SW. (An alternative PP_(a) value=W_(i)/SW is not used in theflowcharts of FIGS. 6 a-7 b.) The PP value specifies the position of apig 20 a on weighing platform 42. The sense of various tests formingparts of the flowcharts of FIGS. 6 a-7 b must be changed if the PP_(a)value is used.

Element 96 also increments an Average Weight Time (AWT) value and aScale Timer (ST) value that indicate elapsed times from the time the AWTand ST values respectively were last cleared. Activity element 96 alsocomputes a new value for a Scale Index SI=current SI+1, and computes anAverage Scale Weight ASW=ΣSW/new SI. The ASW value is the actual averageof SW's read since the ΣSW and SI values were last cleared.

Connector element 98 then returns execution to whatever point in theflowcharts of FIGS. 6 a-7 b the instruction execution was at when theAWD routine started execution. Typically, the animal weighing softwarereturns execution to the software manager every 90-100 ms. or so toallow re-execution of the AWD routine to generate fresh weight values.

FIGS. 6 a and 6 b show the instructions executed for sensing a pig 20 a,etc. moving onto weighing platform 42 and for closing inlet gate 40 whena pig 20 a has progressed sufficiently onto weighing platform 42.

Decision element 110 tests the current SW value against anoperator-entered Minimum Valid Weight value MVW. If SW is ≦MVW, element110 directs instruction execution to activity element 113. Element 113sets a Half Pig Weight parameter HPW=0 and a Scale Timer value ST=0. TheST value is periodically incremented automatically by the AWD routine.

Element 113 also sets an Inlet Flag IF to a first value. Controller 30sets the inlet gate signal on path 65 to the IF value as well, whosefirst value commands inlet gate 40 to the open position. This of courseallows a pig 20 a, etc. to enter passage 31. Instruction execution thenproceeds to the executive routine that restarts the Animal Captureroutine at the next scheduled time.

Eventually a pig 20 a, etc. will enter gate 40 and place at least onehoof on platform 42. The next time the Animal Capture software executionstarts, decision element 110 detects that SW>MVW, and proceeds to nextexecute the instructions of decision element 117.

Decision element 117 tests if the HPW value >0. If so, then executionproceeds through connector element A 118 to decision element 131 in FIG.6 b. The first time this software executes after an animal 20 a placesits hooves on platform 42, the HPW value will still be 0 as set byactivity element 113, so the execution proceeds to decision element 120.

Decision element 120 tests whether the PP value >80%. If so, thisindicates that a pig 20 a has forced its way through the exit chute 32or the exit gate 41 the wrong way, or that only the rear hooves of pig20 a are still on the weighing platform 42, so a valid weighing is notpossible. In this case, the execution proceeds through connector element220 to the Clear Scale routine.

If PP ≦80%, then the decision element 125 instructions execute next.Decision element 125 tests whether the current W_(i) value>previousW_(i) value. If true, then the Animal Capture software executes again.This means the pig 20 a has just stepped on weighing platform 42.

If not true, this means the pig 20 a has taken another step forward onthe weighing platform 42, transferring weight from scale 35 to scale 36,but has not yet stepped onto the weighing platform 42 with either rearhoof. In this case, activity element 128 sets the HPW value to the valueof the SW calculated by the previous execution of the AWD routine, andthe Animal Capture routine executes again. This next execution of theAnimal Capture routine finds decision element 117 directing execution todecision element 131 since the HPW value >0.

Turning next to FIG. 6 b, decision element 131 tests whether the InletFlag IF has its first value. If yes, this means that inlet gate 40 isopen, and the instructions for decision element 145 are executed next.

Decision element 145 instructions test whether current SW >1.33 HPW. Iftrue, this means that a pig 20 a has both front hooves and at least oneback hoof on weighing platform 42. The IF is set to the second (inletgate 40 closed) value to prevent another pig 20 b from entering passage31 and the pig 20 a within passage 31 from backing off weighing platform42. Next, the Animal Capture routine is re-executed. If SW >1.33 HPW isuntrue, the instructions for decision element 149 execute.

Decision element 149 uses the following Position Trigger (PT) table. Useof the PT table provides an alternative basis for making the decision toclose the inlet gate 40.

The PT table specifies for the current SW value a current PP value thatvery nearly guarantees that inlet gate 40 can be closed without hittingthe pig 20 a with gate 40 in a way that may disturb it. The PT tablefollowing has values for feeder pigs, but other tables for other typesof quadrupeds can be developed. The entries in this PT table are basedon measurements of actual pig size and weight.

POSITION TRIGGER TABLE Scale Weight Position Trigger  0-15 26 16-31 2732-47 30 48-63 33 64-79 36 80-95 39  96-111 41 112-127 43 128-143 44144-159 45 160-175 45 176-191 31 192-207 32 208-223 33 224-239 33240-255 34 256-271 35 272-287 36 288-303 37 304-319 37 320 and up 38

Decision element 149 selects the PT value from the PT tablecorresponding to the current SW value. If the current PP value is>theselected PT value, it is very likely that the animal 20 a has clearedinlet gate 40. The decision element 149 provides an alternative basisfor closing inlet gate 40. If the decision element 149 test issatisfied, the instruction execution proceeds to activity element 155 aswith decision element 145.

If the decision element 149 test is not satisfied, the decision element152 executes, testing the ST value. If the ST value is greater than 180sec., controller 30 executes a coax function to urge the pig 20 a tostep onto the scale. A number of different operations beyond the scopeof this invention may comprise the coax function. Then the AnimalCapture routine is re-executed.

If the decision element 131 test is unsatisfied, execution branches todecision element 134. Decision element 134 tests if the PP value is<15%, which if true suggests that the pig 20 a has backed off the scale.In this case, the activity element 142 instructions are executed,resetting HPW=0, ST=0, and the IF to the first value causing inlet gate40 to open. Resetting these values causes the Animal Capture routine tore-execute from the very beginning.

If the PP value is ≧15%, execution branches to decision element 138.Decision element 138 tests whether the current SW value≦the previous SWvalue. If true, this means that a pig 20 a has been completely onweighing platform 42 for at least two executions of the Animal Captureroutine. Execution then branches to the Capture Weight routine atconnector 170 for recording the pig 20 a weight. If SW>the previous SWvalue, SW is still increasing and the Animal Capture routine isre-executed.

FIGS. 7 a and 7 b are the flowcharts for the Capture Weight routine,which verifies that the weight determined is likely to accuratelymeasure the actual weight of the pig 20 a on weighing platform 42.

First, decision element 180 tests whether the AWT value is >1 sec. Iftrue, then the pig 20 a, etc. has been on the scale for at least 1 sec.This means that an adequate number of SW values have been acquired toprovide a good approximation of the pig 20 a weight. In addition, thetests forming a part of the Animal Capture routine have all beensatisfactorily passed, meaning that ASW is an accurate value for theactual pig 20 a weight.

To indicate that ASW accurately reflects the actual pig 20 a weight, theWeight Captured flag previously cleared by activity element 162, is setby activity element 183. Then regardless of the AWT value, decisionelement 186 is executed.

Decision element 186 tests whether ASW is greater than 10%. If so, thissuggests that an indeterminate error has occurred in acquiring eitherthe current values of W_(i) and W_(e) or the previous values of W_(i)and W_(e). In this case, the instructions of activity element 196 areexecuted, which set HPW, ST, SI, and ΣSW values to 0 and set the IF tothe first value, opening the inlet gate 40.

If ΔSW is ≦10%, decision element 190 is executed next, which testwhether SW is <MVW. If so, this means that the value calculated for thecurrent value of SW is below the operator-selected minimum pig weight,and the instructions of activity element 196 are executed.

Next, decision element 193 tests whether PP value <15%. If so, the pig20 a has backed off the weighing platform 42, so the Animal Captureroutine must be run again, and the instructions of activity element 196are executed. If all of these tests are passed, then instructionexecution passes through connector element B 198 to decision element 200on FIG. 7 b.

Decision element 200 tests whether the ASW value>an operator-enteredMaximum Valid Weight. If true, a problem has occurred in acquiring thepig 20 a weight, and instruction execution transfers to decision element217.

If the ASW value is ≦Maximum Valid Weight, then decision element 203tests whether the Weight Captured flag is now set. If so, then theinstructions of decision element 209 are executed.

Decision element 209 tests whether the ASW value<the Minimum ValidWeight. If so, the ASW acquired cannot be trusted to be accurate, andexecution transfers to the Animal Capture routine to begin anotherattempt to weigh a pig 20 a.

On the other hand, if the ASW value has been found to fall within theweight range bounded by the Minimum and Maximum Valid Weight values andthe Captured weight flag is set, then the ASW value can be stored. TheRFID tag is read by activity element 211 and is stored by activityelement 214 along with the ASW and any other pertinent data in memory62. Element 214 forms a second weight recorder. Typically, the weightdata will eventually be transferred to another computer in some way forfurther evaluation.

If the Weight Captured flag is not set, then decision element 203transfers instruction execution to decision element 206, which tests thevalue of the ST. If ST>10 sec., then the pig 20 a has been on theweighing platform 42 for too long, and the instructions of decisionelement 217 are executed next.

If the Weight Captured flag is set, then decision element 203 transfersinstruction execution back to the start of the Capture Weight routine atconnector element 170.

Decision element 217 tests whether SW<Minimum Valid Weight. If so, thismeans the pig 20 a has stepped off the weighing platform 42 and anotherpig 20 a can be weighed when the opportunity presents itself. IfSW≧Minimum Valid Weight, then activity element waits one second andagain executes decision element 217.

Frequently, pig 20 a will stand with all four hooves on weighingplatform 42 for at least 1 sec. to allow ΣSW to be acquired and a validASW available. If this turns out to be only occasionally true, then theexit gate 41 shown in FIG. 1 a may be necessary to allow adequate numberof weight acquisitions over a set time. This will require additionallogic to open and close exit gate 41. In general, this logic willrequire exit gate 41 to close when the front hoof of a pig 20 a is firstdetected on weighing platform 42, and then to open when a valid ASW isacquired.

1. An animal weighing system for use in a pen containing a plurality ofquadruped animals, said pen having at least first and second segregatedspaces with a first one-way chute allowing animal passage from thesecond space to the first space, comprising a) a passage having anentrance and an exit, said passage allowing animal passage from thefirst area to the second area; b) a weighing station within the passage,said weighing station including i) a weighing platform within thepassage and forming a part of the platform and over which an animal mustpass when passing from the first to the second space, said weighingplatform having inlet and exit ends adjacent to the first and secondspaces respectively, ii) an inlet scale supporting the weighing platformadjacent to the inlet end thereof, and providing an inlet weight signalencoding a value indicating the weight supported by the inlet scale, andiii) an exit scale supporting the weighing platform adjacent to the exitend thereof and providing an exit weight signal encoding a valueindicating the weight supported by the exit scale; and c) a controllerreceiving the inlet and exit weight signals and comprising i) a memory,ii) calculation element receiving and recording the inlet and exitweight signals, calculating a plurality of parameters based on the inletand exit weight signal and encoding a scale weight value equal to thesum of values encoded in at least one inlet weight signal and at leastone exit weight signal, and iii) a platform status element periodicallyexecuting an algorithm determining from the values encoded in the inletand exit weight signals the presence of a single animal on the weighingplatform, and responsive to said determination issuing a weight capturedsignal signifying that the scale weight value accurately specifies theweight of the animal on the scale.
 2. The weighing system of claim 1,wherein the calculation element periodically computes a scale weight asthe sum of the current inlet and exit weight values, and a positionvalue as a function of the inlet and exit weight values, and wherein theplatform status element issues the weight captured signal responsive toat least one of i) at least one increase in successive inlet weightvalues, ii) the position value having a predetermined relationship to apredetermined value and the current scale weight being less than theimmediately preceding scale weight, and iii) the position value having apredetermined relationship to a trigger table recorded in the memoryrelating animal length to the sum of the inlet and exit weight values.3. The weighing system of claim 1, wherein the calculation elementperiodically computes a scale weight as the sum of the current inlet andexit weight value, and a position value as a function of the inlet andexit weight values, and wherein the platform status element issues theweight captured signal responsive to at least one of i) at least oneincrease in successive inlet weight values, ii) the position signalvalue having a predetermined relationship to a predetermined value, andiii) the position signal value having a predetermined relationship to atrigger table recorded in the memory relating animal length to the scaleweight.
 4. The weighing system of claim 3, wherein the passage includesan inlet gate respectively opening and closing responsive to first andsecond values of an inlet gate signal, and wherein the platform statuselement further issues the weight captured signal responsive to at leastone of i) the first value of the inlet gate signal and the current valueof the scale weight exceeding the previous value of the scale weight,and ii) the current value of the scale weight being a predeterminedpercentage of the previous value of the scale weight.
 5. The weighingsystem of claim 4, wherein the platform status element further includesan element issuing the inlet gate signal with a second value responsivein part to one of i) the current value of the scale weight being apredetermined percentage of the previous value of the scale weight andii) the position signal value having a predetermined relationship to thetrigger table.
 6. The weighing system of claim 3 wherein the platformstatus element further includes an element issuing the weight capturedflag responsive in part to the inlet gate signal having the second valueand at least one of i) the position signal value exceeding apredetermined value, and ii) the current scale weight being less thanthe previous scale weight.
 7. The weighing system of claim 3 wherein thecalculation element computes the position signal as: one of the inletweight and the exit weight divided by the scale weight.